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AMfone's Online AM Handbook => Hints and Kinks => Topic started by: kf4qkr on June 04, 2013, 12:38:10 PM

Title: Grinding crystals-2
Post by: kf4qkr on June 04, 2013, 12:38:10 PM
I purchased 10 crystals at Dayton that are in the ham bands.5 start in the 75 meter band and 5 start in the 40 meter band.The 75 meter crystals are in the 3.5 to 3.6 range. The 40 meter crystals are in the 7.1 to the low 7.2 range.I used the same method to grind them that I explained in my first grinding crystals post so I am not going to explain everything in this post ,I am just adding a few more things I learned in this experience.Of course I already had a 3885 crystal I ground earlier.I ground 2 of the 75 meter crystals to 3880 and 3875.I over shot the 3880 by 2 kc,s so I used the pencil lead method to get it back to 3880 and I over shot that by 1 kc.I tried to erase the pencil lead with the eraser.DONT TRY THIS the crystal wont work.Wash it off with 91 % rubbing alcohol then start over again.Put a small arrow on the crystal so You can put it in the same way each time because after you mark the crystal with the pencil it makes a difference on the frequency as to which way you put it in the PT-243 holder.This about drove me crazy until I figured out what was going on.I used my favorite 3 by 6 inch knife sharpening stone[which has only been used for crystals] to grind the crystals. I used the figure 8 method and washed the quartz off every time after grinding .See my first post for more details.I now have a 3885,3880,3875.7290 and a 7295 crystal and I have 6 crystals left that have not been ground.It took from 7:30 at night to 3:30 in the morning to grind them and to get them on the proper frequency .It tried my patience and I may have a few more grey hairs  but I got it done.I also over shot one of the 40 meter crystals and had to use the marking with no#2 pencil method to move it back a couple of kc,s. Thought I would share this experience with you guys 73,s   Mike

Title: Re: Grinding crystals-2
Post by: W7TFO on June 04, 2013, 12:50:47 PM
Many thanks.

Is your stone grey or white?


Title: Re: Grinding crystals-2
Post by: kf4qkr on June 05, 2013, 04:00:42 PM
The stone I am using is dark grey.On a footnote last night I was grinding some more of my crystals and one of the crystals was 3509 . I got it to about 3843 and started to grind it some more and it quit working so I guess there is a limit to how far you can grind them.So far I have not had a problem grinding them 2 meg's. 7 out of 8 have been succesful.I will let you all know how the last 2 go.      Mike

Title: Re: Grinding crystals-2
Post by: W7TFO on June 05, 2013, 04:34:19 PM
I've heard the center axis gets lopsided and they quit.

I guess you have to try and do both sides equally.


Title: Re: Grinding crystals-2
Post by: N4zed on June 08, 2013, 04:21:31 AM
All you ever wanted to know about making crystals.... (


Title: Re: Grinding crystals-2
Post by: kf4qkr on June 11, 2013, 01:49:18 PM
I am finaly done 9 out of 10 were successful. I have more 7290's than I need so I will give a freind one. I over shot one of the 3885's to 3886.5 .I will just keep it, there might be some reason I might need to transmit there some day.3885,3880,3872, 7290and 7295 are covered now with some extra backups.I have a vxo adapter I built that you plug the crystal in and plug the adapter in the socket on the rig and you can adjust the trimmer cap and slide down 5 to 7 kc,s before it starts to get flakey so 3870 is covered and all frequencys in between the crystals frequency are covered.Yes I know what a vfo is but this is more fun.        Mike

Title: Re: Grinding crystals-2
Post by: W7TFO on June 11, 2013, 02:12:34 PM
Rocks are so organic :).

VFO's are, well. machines :-\

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